Attorney: For death penalty to be considered, charges must show more than negligence

It's a tragedy that has made many people across the country sick to their stomachs. A Georgia father said he drove to his job in suburban Atlanta June 18, parked and worked a full day only to return to his car and find that he'd forgotten that his infant son was in the back. Cooper, 22 months, was dead. Temperatures that day had soared to 92 degrees.

There have been a lot of twists and turns in the case involving Justin Ross Harris, who is facing murder and child cruelty charges. The 33-year-old has pleaded not guilty. At a hearing July 3, one of the story's most sensational details emerged: the prosecution's lead investigator testified that while Harris was at work and his son was dying in the car, the father sent explicit messages and exchanged texts with six women. Harris also sent a picture of an erect penis to an underage female, Cobb County Police Detective Phil Stoddard testified.

On Tuesday, CNN affiliate WXIA reported that investigators returned to Ross Harris' job location to recreate the conditions of the day that Cooper died.

Cobb County Police spokesman Michael Bowman told CNN that the department "turned over" Harris' vehicle that morning to the Cobb County District Attorney's Office for "heat testing" and it was returned Tuesday evening. No Cobb County police officers were at the scene when the testing happened, Bowman said, and the results of test will stay with the district attorney's office.

Bowman also told CNN Wednesday that a toxicology test was administered on Cooper's body, but those results are not yet available.

While the temperature on the day Cooper died was around 92 degrees, CNN weather experts believe temperatures could have climbed to nearly 140 degrees inside the car.

New documents released this week

Documents released Monday revealed more details of the investigation.

The documents, which included applications for search warrants and eight actual search warrants in the case against Harris, seek the medical records of Ross Harris and his son, a DVD, a 2-gigabyte memory card, a 32GB thumb drive and an external hard drive.

According to Stoddard, before Cooper Harris' death, the boy's father visited a Reddit page called "child-free" and read four articles; he allegedly searched online about how to survive in prison and how hot a car needs to be to kill a child. It wasn't clear from Stoddard's testimony exactly when these searches took place.

When does a grand jury come in?

Investigators continue to search through evidence and conduct interviews.

When they're done, law enforcement will hand over its findings to the prosecutor's office, which will present the case to a grand jury. Sources tell CNN that it may be late July before the grand jury makes a decision.

Cobb County District Attorney's Office spokeswoman Kim Isaza told CNN Wednesday that ethical standards bar the prosecutor's office from commenting on evidence in the case. "This case will run its course and we will follow wherever the evidence leads us," she said.

What about Cooper's mother?

On Tuesday, Leanna Harris, who has not been named as a suspect in her son's death, visited her husband at the Cobb County Jail, according to CNN affiliate WXIA.

It's unclear whether she was able to talk to him.

Citing the ongoing investigation, Cobb County Sheriff spokeswoman Nancy Bodiford told CNN the department wouldn't release details about any visitors Ross Harris has. Bodiford also said the department would not release audio of phone calls Harris receives or describe conditions of his confinement.

Any communication the couple has at the jail will be recorded, Atlanta attorney Page Pate said on CNN Wednesday. Page is not associated with the case.

On Thursday, Cobb County attorney Lawrence Zimmerman told CNN that Leanna Harris has hired him, adding that he is not speaking to the media at this time.

There's not much publicly known about his client. The 30-year-old dietitian is licensed in Georgia and Alabama, records show, and she has lived in Georgia since 2012. Before moving to the Atlanta suburb of Marietta, Leanna Harris lived in Moundville, Alabama, a town of about 2,400 people south of Tuscaloosa.

She married Ross Harris May 7, 2006, in Tuscaloosa where her husband worked as a police dispatcher from June 10, 2006, to May 22, 2009.

Leanna spoke at Cooper's funeral in Tuscaloosa, calling her baby boy "perfect" and saying that she would not trade "mommy time" for "the world."

"I miss my son," she said, "and I will miss him forever."

Wife can be compelled to testify against husband

Five days before Cooper died, authorities say Ross Harris twice viewed a video posted on YouTube in which a veterinarian demonstrates the dangers of leaving someone or something inside a hot car.

Leanna Harris told police that she had recently seen a story on a state initiative aimed at reminding people not to leave children in cars and that doing that was a fear she had, Stoddard testified.

In some criminal cases, a spouse cannot be compelled to testify against the other. However, in Georgia, if the charges allege wrongdoing involving a minor, a husband or wife can be forced to testify against their spouse.

The case and the death penalty

In Georgia, the child cruelty charge carries a penalty of five to 20 years behind bars. If Ross Harris is convicted of murder, he could get life, life without parole or the death penalty. If a person commits a felony and that act results in the death of someone -- whether it's intended or not -- that person can be charged with felony murder.

A murder can qualify for the death penalty in Georgia if it was "outrageously or wantonly vile, horrible, or inhuman in that it involved torture, depravity of mind, or an aggravated battery to the victim," according to criminal attorney Philip Holloway, who has served as a legal commentator about the case on CNN.

In order to meet that threshold, the evidence will need to demonstrate more than criminal negligence. The current warrant is merely a preliminary charging document. The district attorney can upgrade the charges when the case is presented to the grand jury for indictment, he said.

The Harris' church calls for 'justice'

On Sunday, Stonebridge Church in Marietta -- where the Harris family attended -- presented a sermon asking that the congregation pray for "truth and for mercy and for justice."

"Many continue to ask just how to love on Ross and Leanna right now," a minister can be heard saying in a sermon posted online. "I would say micro level, very close, it's all of the same stuff. Legally, all of that's out of our hands.

"We're just praying for truth and for mercy and for justice," the sermon continued. "Those are attributes of God, and we're just praying, continuing to pray through this whole legal process that those three things would be evident. That's God's character, and you can pray confidently for truth and for justice and for mercy, and I would say relationally, for opportunities to love them, whatever that looks like."